Macromolecular construction has evolved to include utilitarian composite materials whereby interdependent components are precisely matched for desired physicochemical properties. Targeted materials and properties, derived from minimum-assembly protocols, are desirable due to a variety of considerations, including economic viability, ease of construction, and enhanced scale-up potential. Thus, supramolecular and iterative-based chemistries converge in rational fractal designs; whereby, molecular architectures exhibit self-similarity on differing scales to provide a balance of interrelated attributes and structural components. Research efforts in our laboratories suggest that fundamental supramacronmolecular properties can be affected by subtle changes in design parameters.
The use of ligand-metal-ligand connectivity has served to expand the directed and self-assembly work into the novel, utilitarian “fractal” macro- and nanomolecular architecture arena. These constructs have led to the development of materials with demonstrated potential as energy storage and release devices based on stable oxidized and reduced metal states, as components of molecular devices, such as in new photovoltaic cells and organic light emitting diodes (OLEDs), based on their photo- and electroluminescence properties, and as molecular switches, foundations for information storage and retrieval, and optical display components, based on their low spin-high spin characteristics predicated on the light-induced excited spin-state trap (LIESST) effect.
The past several years have witnessed increased interest in the general topic of metallo-fractal materials, particularly in relation to their future nanotechnological applications. These directions have been built on the melding of classical synthetic strategies with materials science construction and characterization protocols to “tune” bulk and localized supramolecular properties to specific tasks, and to assemble macromolecular infrastructures capable of functioning alone or in concert within materials at composite interfaces.
Considering the constant quest for new monomers, the ability to incorporate specifically directed metal centers, and structural components that can facilitate access to application-oriented architectures, as well as innovative construction protocols, we herein demonstrate the construction of new nanomolecules predicated on: (1) the self-assembly of fractal-based materials to allow access to network-based architectures utilizing new materials and composites with enhanced functional properties; (2) ametal-ligand assembly employing preconstructed synthons to facilitate the generation of nano- and macroscopic, precisely positioned, dual and polymetal arrays giving rise to new multicomponent macromolecular systems; and (3) targeted assembly of ordered aggregates of fractal-based architectures possessing polymetallic subunits that facilitate the selective construction of a desired pattern out of the many different network patterns.